Sheet edging apparatus

ABSTRACT

Edge treating belt-grinder units are provided to produce, in sequences of operation, a desired ground surface on, for example, the lower corner, the upper corner and the vertical surface of a sheet or plate of glass. The glass is moved along a definite path and the abrasive belts are mounted for movement toward and away from the path. Monitoring elements act to control the grinder units in accordance with detected position and contour changes of the glass sheets.

United States Patent 1151 3,673,737 Welker et al. July 4, 1972 54 SHEET EDGING APPARATUS 1,933,640 11/1933 Schafer ..51 40 791,897 6/1905 .51/80 A [72] Inventors. Robert H. Welker, Perrysbur William L.

l-lelmbrecht, Toledo, both of ghio 2560740 7/1951 51/80 A X 2,671,992 3 1954 Reaser ..51/80 A [73] Assignee: Libbey-Owens-Ford Company [22] Filed: May 4, 1970 [2]] Appl. No.: 34,278

[52] [1.8. CI ......5l/38 [5]] Int. Cl 1 ..B24b 21/16 [58] Field of Search ..5 l/38-39, 76 R,

[56] References Cited UNITED STATES PATENTS 3,562,961 2/197] Clayson ..5l/l38 3,566,546 3/1971 Lindmark ..5l/l42 X Primary Examiner-Donald G. Kelly Attorney-Collins and Oberlin [57] ABSTRACT Edge treating belt-grinder units are provided to produce, in sequences of operation, a desired ground surface on, for example, the lower corner, the upper comer and the vertical surface of a sheet or plate of glass. The glass is moved along a definite path and the abrasive belts are mounted for movement toward and away from the path. Monitoring elements act to control the grinder units in accordance with detected position and contour changes of the glass sheets.

8 Claims, 15 Drawing Figures PATENTEDJUL '4 I972 SHEET 10F 6 mmq 00w w wm ax m3 5 3m 2 NS Pm u Hm 0mm A N w $3 3$ M M tum QM? mam mm? Om raw 0m OW 0: l/Om how 01 mz omu N wm 0 h 03 5m mmm PATENTEDJUL 4 1972 3.673 .737

sum u or a ass 223 zao 21a zse 235 INVENTORS Qade/ctfl. wan and (e/wzm {filmmnz ATTORNEYS SHEET ammo APPARA'I'US FIELD OF THE INVENTION In the manufacture of sheets or plates of glass for ultimate use in the automotive industry, it is customary practice to convey a plurality of sheets in a straight forward path along which a variety of treating apparatus is located to act upon the sheets and/or edge portions in a substantially automatically controlled manner. Many of such sheets are pattem-cut to outlines conforming to the form and location of window openings of an automobile and consequently with an increase in the area required for some sheets there has also been developed a number of outlines at least one marginal portion of which may or will include one or more inwardly curved areas. To handle the edge treatment or belt grinding of these edge areas as well as substantially flat marginal edge portions, there is provided novel control means for presenting an abrasively surfaced grinding belt to the edge of a glass sheet and thereafter ensuring that the belt surface will follow the exact surface of the edge.

This invention therefore has particular reference to an improved control for glass edge treating apparatus which employs a driven grinding or abrasive belt. I

It is an.important object of the invention to provide improved edge treating apparatus including at least one beltgrinder type edging unit and having control means that is par ticularly adapted to ensure satisfactory treatment of the edges of a glass sheet of large size and irregular outline.

Another object of the invention is to provide edge treating apparatus of the above character employing a plurality of edge treating units, each utilizing a belt-type grinding means to treat a selected portion of the edge of a sheet and a control means associated with each unit including a roller having a vertically disposed surface movable into tangent relation to the edge of a sheet to define the point of tangency of the grinding means.

Other objects and advantages of the invention will become more apparent during the course of the following description when read in connection with the accompanying drawings.

In the drawings wherein like numerals are employed to designate like parts throughout the same:

FIG. 1 is a side elevation of a grinding apparatus constructed in accordance with this invention;

FIG. 2 is an end elevation of the apparatus;

FIG. 3 is a view of a horizontal section taken on the plane of line 3--3 in FIG. 1;

FIG. 4 is a view of a transverse vertical section taken on the plane of line 4-4 in FIG. 1;

FIG. 5 is a fragmentary view of the upper part of the apparatus as viewed in FIG. 4;

FIG. 6 is a view of a transverse vertical section taken on the plane of line 6-6 in FIG. 1;

FIG. 7 is a fragmentary view of the upper part of the apparatus as viewed in FIG. 6;

FIG. 8 is a view of a fragmentary elevation of the reverse side of the apparatus;

FIG. 9 is a view of a sectional detail of the belt systems for conveying sheet materials taken on the plane of line 9-9 in FIG. 1;

FIG. 10 is a perspective view of an element of the belt system;

FIG. 1 1 is a detail view of an electric control device;

FIG. 12 is a view of a transverse vertical section taken on the plane of line 12-12 in FIG. 1;

FIG. 13 is a view of a horizontal section taken on the plane of line 13-13 in FIG. 12;

FIG. 14 is a view of a horizontal section taken on the plane ofline 14-14 in FIG. 12; and

FIG. 15 is a diagrammatic view of a control system for the apparatus.

DETAILED DESCRIPTION OF THE INVENTION With reference now to FIG. 1 of the drawings, grinding apparatus constructed in accordance with the instant invention includes a plurality of edge treating units arranged in tandemwise relation to one another and adapted to treat, by way of example, the upper comerof the edge of a sheet, the lower comer and the vertical surface of said edge as the sheet is progressively moved therepast by the substantially endless belts of a conveyor system associated with the apparatus. The apparatus is structurally embodied in a framework, generally designated by the numeral 20 and the conveyor system is similarly designated by the numeral 30. With the sheet material, such as sheets or plates of glass S, being moved in the direction of the arrow indicated by the letter F from the entry end of the apparatus (FIG. 1), the first edge treating unit is designated in its entirety by the numeral 400, a second unit by the numeral 40b and a third unit by the numeral 400.

STRUCTURAL FRAMEWORK Referring more particularly to the framework 20, as best illustrated in FIGS. 1 and 2, there is provided a framing member 200 at the entry end of the apparatus which includes pedestals 201 and 202, based on floor plates 203, with an integral vertically disposed channel member 204 rising from the pedestal 201 and a similar channel member 205 rising from the pedestal 202. The pedestals 201 and 202 are fixed in spaced relation by a transversely disposed beam 206 while the channels 204 and 205 are interjoined by horizontally disposed channels 207 and 208. The duplicate framing member 210 at the exit end of the apparatus includes pedestals 211 and 212, based on floor plates 213, with vertically disposed channel members 214 and 215, respectively, similarly rising therefrom. Pedestals 211 and 212 are fixedly interconnected by a bracing member 216 and the channel members 214 and 215 by transversely arranged horizontal channels 217 and 218.

The channel members 204 and 214 are joined by a longitudinally disposed beam 220 which is supported on the channel members by fixed posts 221. In inwardly spaced relation from the frame members 200 and 210, the beam 220 supports an end of transverse, horizontally disposed beams 222 and 223 which at their opposite ends (FIGS. 2 and 6) are carried by floor based columns 224 and 225. A beam 227, in substantially the same horizontal plane as beam 220, is integrally joined with the columns 224 and 225 while a reinforcing member 228 is similarly joined therebelow. In inwardly spaced parallel relation with regard to the beams 222 and 223, a pair of beams 230 and 231 are structurally carried by the longitudinally disposed beams 220 and 227. The beams 222, 230, 231 and 223 serve as support elements for longitudinally disposed beams 232 and 233.

Also included in the general structure of the framework 20 are a pair of channel members 235 equally spaced from the longitudinal axis of the framework and mounted at their respective ends on plates 236 supported on the floor plates 203 and 213. In similarly spaced relation, a pair of channel members 238 are supported at their ends on the transversely disposed channels 208 and 218. These pairs of channel members are adapted to serve as support mediums for the conveyor system 30 as will shortly be explained.

CONVEYOR SYSTEM As here employed, this conveyor system comprises a lower pair of substantially endless belts 300 and an upper pair of belts 301. Generally speaking, each of the belts is of roller chain with the individual links 302 (FIGS. 9 and 10) being formed with bent lug attachments 303. Rubber blocks 304 having alternately notched or saw-tooth" ends are adhered to plates 305 that are secured as by bolts 306 to the bent lugs 303 of the chain links. As viewed in FIG. 1, the pairs of roller chain belts 300 and 301 are entrained about suitably mounted sprockets to traverse substantially rectangular paths of movement.

While traversing the upper run of the continuity of belts 300 and lower run of the continuity of the belts 301, the blocks 304 by their opposed surfaces (FIG. 9) provide cushioned but firm mediums for supporting the sheets S and moving them forwardly past the edge treating units 40a, 40b and 400. For this purpose, a pair of double-track members 310 and 311 is longitudinally disposed between the frame members 200 and 210 superimposed one above the other. The track member 310 is supported adjacent its ends by angle members 312 attached structurally to the channel members 204-205 and 214-215. On the other hand, the track member 311 is downwardly spring-biased to resiliently urge the blocks in the lower run of the pair of chain belts 301 against the upper surface of a glass sheet and thereby maintain the blocks in the upper run of the chain belts 300 in active engagement with the lower sheet surface. To this end, each track of the members 310 and 311 is equipped with a bar 314 on and against which the rollers of the chain belts are in contact. The firm pressure to be exerted by the blocks 304 is adjustably obtained by the mounting of the track member 311 which, as shown in FIGS. 1 and 6, is supported at its ends by plates 316 equipped with threaded rods 317. The rods 317 are passed through angle members 318 structurally carried by the channel members 204-205 and 214-215 and equipped with nuts 319. By means of the nuts 319, springs 320, interposed between the plates 316 and angles 318, are adapted to urge the track member 31 1 downwardly. To maintain this resiliently spaced relation, pairs of channels 322 and 323 are carried by the track members with threaded rods 324 and springs 325 serving the same purpose. 7

The pairs of roller chain belts 300 and 301 are operatively driven from a common source of power such as a so-called line shaft 327 which serves to additionally operate other aligned apparatus through which the sheets are passed for further processing. The shaft 327, as in FIG. 1, is adapted to drive a gear unit 328.

With reference to the chain belts 300, the same are entrained about pairs of sprockets 330, 331, 332 and 333; each pair being keyed on a related shaft 334, 335, 336 and 337. The shaft 334 is joumaled in bearings 339 mounted on pedestals 211 and 212while the shaft 335 is joumaled in tensioning bearing members 340 on the pedestals 201 and 202 (FIG. 2). The shaft 336 is joumaled in bearings 342 mounted on brackets 343 supported on the upper ends of the pedestals 201 and 202. In similar manner, the shaft 337 is joumaled in bearings 345 on brackets 346 at the upper ends of pedestals 211 and 212.

The pair of roller chain belts 301, in like manner, is entrained about pairs of sprockets 350, 351, 352 and 353; each pair being keyed on a related shaft 354, 355, 356 and 357. The shaft 354 is joumaled in bearings 357 supported by brackets 358 on the channel member 217 while the shaft 355 is journaled in like bearings 359 supported by brackets 360 on the channel 207. The shaft 356 is joumaled in tensioning bearing members 361 on plates 362 at the upper ends of channel members 204 and 205. Similarly, the shaft 357 is carried by bearings 363 mounted on plates 364 at the summits of channel members 214-215.

It will be apparent that the gear unit 328 is adapted to drive a chain belt 366 which, with regard to FIG. 8, is entrained about a sprocket 367 keyed on shaft 334. This provides the operative drive for the pair of belts 300 with the pair of belts 301 being driven through a chain belt system from the shaft 337. Thus, shaft 337 has keyed thereon a sprocket 370 about which a chain belt 371 is entrained. Since the pair of belts 301 move in reverse order to movement of the pair of belts 300, provision is herein made to entrain the chain belt 371 about sprocket 372 on a shaft 373, joumaled in bearings 374 generally mounted on the channel members 215-217 and equipped with a fixed pinion gear 376. This gear meshes with a pinion gear 377 keyed on the shaft 354 which is thereby joumaled in bearings 387 mounted on the channels 238.

As the sheets of material, such as sheets or plates of patterncut glass, pass from a conveyor system, shown by broken line I and designated by the numeral 389 in FIG. 1, they are received in the entry end of the apparatus on a roller 390 having a shaft 391 journaledin bearings 392 suitably supported on the channel members 204-205. The roller 390 is adapted to be driven through a chain belt 393 entrained about a v sprocket 394 fixed on the shaft 391 and a sprocket 395 on the shaft 336 on which the sprockets 332 are keyed. At the exit end of the apparatus, a similar roller (not shown) is mounted on shaft 396 (FIG. 8) having a sprocket 397 keyed thereon and driven from a sprocket 398 on the shaft 337 by a chain belt 399 trained thereabout. Emerging from the apparatus, the sheets are received on a conveyor indicated in broken line and designated by the numeral 389.

THE EDGE TREATING UNITS Generally stated, each of the edge treating units, designated generally by the numerals 40a, 40b and 40c, is of the same physical structure although as the description proceeds, differing numerals will, in certain instances, be employed with regard to each unit. One novel aspect of the invention is believed to reside in the manner in which each unit is selectively moved forwardly to present the abrasive surface of the working run of an associated grinding belt to an'edge of the glass sheet and then moved rearwardly. As the abrasive surface is brought into active engagement with a selected portion of the sheets edge, an exact degree of contact is established by the use of a monitor system including a control roller that is adapted to engage the sheet edge and thereby ensure that the belt surface will neither be objectionably urged against the said edge nor prevented from desirably carrying out the abrasive treating action. In one instance over" engagement of the belt could bring about anexcessive grinding action and early loss of the belt and in a second instance, under engagement could prevent any'effectiveness of the grinding actionwith a resultant improperly finished edge surface. Moreover, the control roller and the monitor system, about which more will be said later, make possible the desired treating of the edge of a pattem-cut sheet such as is shown by wayof example in broken line in FIG. 3. Thus illustrated, the sheet is typical of such outlines as those to which a sheet or plate of glass is pattern-cut for eventual use in the automotive industry. In treating the proximate edge of the sheet, the monitor system will be active to maintain the control roller in rolling contact with the edge to follow therealong as into, through and out of the curvedly shaped entrant area A as shown. As broadly indicated in FIG. 3, the roller of the monitor system, generally designated by the numeral 50, is moved from the full line position to a position of tangency with the sheet edge, as indicated in broken line, which will ensure that a tangency line, indicated by the letter G1, of the belt surface will be brought into effective engagement with the appropriate comer or vertical edge surface of the sheet, as indicated by the letter G2.

As seen in FIGS. 1 and 2 of the drawings, the first edge treating unit 40a is located adjacent the entry endof the apparatus and is generally oriented in a selected angular posture such that the working run of the abrasive surface of the associated belt will be effective to finish the upper corner of a sheets edge. This unit, and the units 40b and 400, has a carriage, generally designated by the numeral 400, that includes a major support platform 401 having parallel bars 402 fixed to its upper surface. A pair of sleeve bearing members 405 is mounted on the bars 402 and arranged in spaced parallel relation to the axis of the carriage which is transverse to the longitudinal axis of the apparatus. Each bearing member 405 is slidably supported on an annular rod 406; each rod in turn being supported adjacent its ends by blocks 407. These blocks are structurally attached to the beams 232 and 233. The carriage 400 is adapted to be bodily moved forward and back relative to the rods 406 by means of a cylinder actuator 410, as in FIGS. 5 and 7; having the head end supported on a bracket 41] mounted on the beam 233 and with the rod 412 of its contained piston attached to a bracket 413 mounted on a bar 402. The function of cylinder 410 to move the carriage 400 will be more fully explained in connection with FIG. which discloses an electrically controlled pressure system typical to each of the edge treating units.

The motor for operating the abrasive belt and the idler pulley therefor are associated with a frame member 415 that is supported from the platform 401 by way of a pivotal mounting arrangement. Thus, a U-shaped bracket 416 is secured, as by bolts, to the undersurface of the platform and has downwardly directed walls 417. The walls 417 have aligned downwardly inclined notches 418 for supporting of a shaft 419. A bracket 420 attached to the body portion of the frame member 415 of the unit 40a is carried by the shaft 419 and is locked to the bracket 416 by bolts 422 passed through arcuate slots 423 in the walls 417 and threaded into the bracket 420. In this way, the frame member of the unit can be positioned in the desired angular plane with reference to the best angle at which the working run of the abrasive surface of the belt is to be presented to the edge of the sheet.

The member 415 has at one or its rear end a plate 425 on which the motor 426 is mounted and has provision at its opposite end for pivotally supporting a yoke-shaped arm 427 on which a shaft 428 for the idler pulley 429 is carried. The arm is connected by a link 430 to the rod of a cylinder 43] having connection to a hand control valve 432 by way of tubings 433 and 434. Now, the tautness of the grinding belt 435, trained about a drive pulley 436 on the output shaft of motor 426, and the idler pulley 429, can be maintained by the direction of pressure through tubing piece 434 to the head end of the cylinder 431.

Generally speaking, the cylinder 410 of each treating unit is caused to move the respective carriage 400 forwardly in response to operation of an electric switch 505, carried by a plate 506 on the track member 310, as in FIGS. 3 and 11, when a sheet or plate of glass produces downward deflection of the arm 507. In one way or another, the monitor system 50 causes pressure to be directed to the cylinder with resulting forward movement of the carriage until the aforementioned control roller 500 engages the edge of the sheet. This is indicated by the positions indicated in full and broken lines in FIG. 3 and at which time the area of the working run of the grinding belt will be advanced from the line, designated by the letter Gl,-to engage the sheet edge E as indicated at G2. As shown in FIG. 2, a grinding action of the belt of the treating unit 400 is carried out on the upper corner of the edge. Upon release of the switch arm 507, the cylinder is caused to move the carriage 400 rearwardly to that position shown in FIG. 2.

As shown in FIGS. 4 and 5, the carriage 400 of the edge treating unit 40b is mounted by sleeve bearings 405 on rods 406 supported by blocks 407 on the beams 232-233 between the transverse beams 230 and 231. The frame member 415 of unit 40b is supported by bracket 420!) on the bracket 416 so that it will be located to present the working run of the associated belt 435 to the lower corner of the edge E of the sheet. Also, the control roller 500 of the monitor system associated with the edge treating unit 40b is adapted to control forward movement of the unit when the said working run of the grinding belt has reached a point of tangency with the lower comer of the edge E.

As viewed in FIGS. 6 and 7, the carriage 400 of the edge treating unit 400 is adapted to support the associated frame member 415 in a substantially vertical position upon securement of the bracket 420c to the bracket 416 by bolts 422. This will locate the associated grinding belt 435 so that the working run thereof will act upon the vertical surface of the edge E of the sheet. In FIG. 7, it will be seen that this carriage 400 by sleeve bearings 405 is supported on the bars 406 that are mounted by blocks 407 on the beams 232-233 between the transverse beams 223 and 231.

With reference to FIGS. 12, 13 and 14, the monitor system 50 associated with each of the edge treating units, includes a valve 510 that is mounted by a fixture 511 that is secured to a bracket 512 attached to the plate of each carriage 400. The valve is adapted to be actuated by the control roller 500. To this end, the roller is supported on a lever 515 by a rod 516; said lever being carried on a shaft 517, adjacent its lower end. The shaft 517 is joumaled in bearings 518 mounted on the vertical wall 519 of the fixture 511 and has an actuator bar 520 fixed to its upper end. The bar 520 is held in active contact with the spring-biased plunger 522 of the restrictor valve 510 through the action of a coil spring 523 connecting to a second lever 524 on the shaft 517 and an angle piece 525 secured to the vertical wall 526 of the bracket 512. In this respect, the restrictor valve 510 is adapted to permit full flow of a pressure medium, such as air, therethrough or controllably vary the influence of such pressure. As illustrated in FIG. 14, the control roller 500 is carried by a forwardly advancing carriage 400 until it is brought into contact with the edge E of a sheet as indicated in broken line designated by the numeral 500a. Continued movement of the carriage causes the roller to swing the lever 515, against the action of the spring 523, such as to a second position of the roller indicated by way of example at 500b, at which time the surface of the belt, designated by the letter G2, is brought into engagement with the edge E. This causes the bar 520 to cause action of the plunger 522 to regulate the amount of pressure directed to the associated cylinder 410 and thereby reduce movement of the carriage while maintaining the control roller and grinding belt effectively against the edge of the sheet. In the event that this edge of the sheet includes an inwardly curved area A, as in FIG. 3, as the control roller is caused to follow the curvature of the edge, the lever 515 will permit the spring 523 to reversely swing the shaft 517 through the lever 524. This will affect action of the bar 520 on the plunger 522 with resulting increase in pressure through the valve 510 and forward movement of the carriage. The roller is again forced rearwardly, as to the position 500b, to diminish the pressure as it traverses the following substantially flat portion of the edge.

This manner of action is illustrated diagrammatically in FIG. 15 wherein it will be noted that application of pressure via the valve 510 is controlled to a solenoid-type self-reversing supply valve 530 connected to a source of pressure by pipe 531. Normally, pressure is directed from valve 530 by pipe 532 through the valve 510 by a pipe 533 connecting to the rod end of a cylinder 410. This will hold the carriage 400 in the idle or rearward position such as is indicated by the positions of the units 40a, 40b and 400 in FIGS. 2, 4 and 6, respectively.

When a sheet is approaching each of the units, in succession, and depresses the arm 507 of a related switch 505, an electrical circuit is completed from a source of electrical energy 535 by lines 536 and 537 through the valve 530 and line 538 to the opposite source 539. Upon action of the valve, pressure from supply pipe 531 will be directed through pipe 534 to the valve 510 and thence by pipe 541 to the head end of cylinder 410. Substantially simultaneously, the circuit of line 537 is completed by line 542 to a timing relay 543 through a starter circuit by way of line 544. The timer when thus activated initially functions to break the circuit of lines 542-544 and then establish an overlapping circuit to line 537 by line 545.

As explained in connection with FIG. 14, a required amount of pressure to the head end of the cylinder 410 produces forward movement of the carriage, control roller 500 and grinding belt 435 until the roller is brought into contact with the edge of the sheet as indicated by the position designated by the numeral 5000. Now, continuance of pressure into the cylinders head end will cause the roller and lever 515 to be swung rearwardly to the second position indicated by way of example by the numeral 50%. This swinging of the lever is reflected in a sufiicient amount of rotation by the shaft 517 to change the influence of the bar 520 on the spring-biased plunger of the valve 510. In consequence, the degree of pressure exerted by the pressure medium through pipe 541 will be diminished to a degree only required to maintain the roller 500 and belt 435 firmly against the edge E of the sheet. Of course, as this degree of pressure will temporarily rise as the roller traverses the edge of an inwardly curved wedge or otherwise irregularly shaped area and the bar 520 is accordingly swung to control the plunger 522.

Whatever the configuration of the edge adjacent the trailing end portion of the sheet, the action of the belt must be continued until the said end is therepast. Thus, when the arm 507 of the related switch 505 is released and the circuit of lines 536-537 thereby opened, the circuit from the relay 543 through line 545 serves to maintain the circuit through the valve 530. After a selected interval of time for treatment of the trailing end portion to be accomplished, the relay times out to open the circuit of line 545. The valve 530 thereupon is caused to reverse the direction of pressure from pipe 534 to pipe 532 through valve 510 to pipe 533 and the rod end of the cylinder 410 which will produce rearward movement of an edge treating unit. As the roller is withdrawn from the edge of the sheet, the coil spring 523 contracts to return the shaft 517 and lever 515 to their original position.

MODE OF OPERATION As hereinabove described, the apparatus of this invention includes a framework on which the edge treating units 40a, 40b and 40e are movably supported. in following sequences of individual operation, the units produce the desired ground surface on, for example, the lower corner, the upper comer and the vertical surface of a sheet or plate of glass.

Although not shown in the drawings, it is customary for each of the sheets while on a conveyor, such as designated at 389 in FIG. 1, to be shifted transversely of its movement by an aligning device to locate a succession of sheets with the edge to be treated in a straight forward path. As a sheet is thus received on and passes over the roller 390, the surfaces thereof are engaged by the blocks 304 of the pairs of conveyor belts 300 and 301. The leading end of the sheet then causes closure of a first switch device 505 associated withthe solenoid valve 530 of the edge treating unit 40a. Normally, the valve 530 connects the supply pipe 531 through pipe 532, valve 510 and pipe 533 to the rod end of the cylinder 410. This maintains the edge treating unit 400 and abrasive belt 435 in an inoperative, rearward position with regard to the path of sheet movement. However, switch device 505 activates the valve 530 to connect supply pipe 531 through pipe 534, the valve 510 and pipe 541 to the head end of the cylinder actuator 410. In consequence, the carriage 400 of the unit 40a is caused to move the frame 415 and belt 435 forwardly toward the path of sheet movement. The roller 500 initially contacts the edge of the sheet, as discussed in connection with FIGS. 3 and I4, and the forward movement of the unit carriage produces rearward swinging movement of the levers 515 and 524 whereupon the shaft 517 is rotated, against the action of coil spring 523, to reduce the pressure of the actuator bar 520 on the plunger 522 of the valve 510. The pressure in pipe 541 is thereby reduced to an amount sufficient to maintain the abrasive surface of the belt 435 in active engagement with that portion of the edge of the sheet, such as the lower comer, to carry out the desired degree of grinding.

As the roller 500 follows the edge along and into an inwardly curved or irregular area, as indicated by the letter A in FIG. 3, it temporarily causes the lever 515 to swing the shaft 517 for the valve 510 to sufficiently increase the amount of pressure to the head end of the cylinder actuator to move the roller forward and thereby maintain the surface of the belt against the lower corner of the edge. This increase of pressure is, of course, modified as forward motion of the unit causes the roller to swing the lever 517 rearwardly.

To prevent separation of the belt surface from the sheet edge, the switch device 505 can be held closed until the belt approaches the trailing end of the sheet or, as herein provided, a timing relay 543 can be employed to monitor an interval of time sufficient for this purpose. Thus, when the relay times out, electric control of the solenoid valve 530 is terminated and it self-reverses connection of the supply pipe 531 from pipe 534 to pipe 532 and through the valve 510 and pipe 533 to the rod end of the cylinder actuator 410. Initially, contact of the roller 500 is slowly retracted from the edge of the sheet which permits the spring 523 to swing the shaft 517 by the lever 524 to increase the action of the actuator bar 520 on the plunger 522 of the valve 510. Pressure will thus be increased to remove the surface of the belt from the sheet and the unit 400 bodily to be moved rearwardly.

Now, as a second switch 505, associated with the edge treat ing unit 40b, is engaged by the leading end of the glass sheet, the resulting direction of pressure to the head end of cylinder 410 of the unit 40b produces forward movement of the respective frame 415, belt 435 and roller 500. Contact of this roller will produce a course of action similar to that above set forth with regard to the edge treating unit 40a. In this event, the upper edge comer of the edge of the sheet will be treated. This is also true with respect to closure of a third switch device 505 with resultant operation of the edge treating unit 400 to grind the vertical surface of the edge. Upon completion of the edge treating operation, the sheet is carried through the exit end of the apparatus and received on a conveyor designated in FIG. 1 by the numeral 389'.

We claim:

1. ln apparatus for edge treating glass sheets which includes means for moving said sheets along a definite path, a tool having an abrasive surface mounted for movement toward and away from said path, and means for driving said tool to move said abrasive surface relative to said path; the improvement which comprises monitoring means operable when one of said glass sheets reaches a predetermined position in said path to move said tool under pressure toward said path and for reducing said pressure when said tool is in working engagement with an edge of one of said sheets, said monitoring means including a follower adapted for moving engagement with said sheet edge.

2. Apparatus as defined in claim I in which said monitoring means includes means for holding said tool away from said path under pressure when none of said sheets has an edge in position for working engagement thereby.

3. In apparatus for edge treating glass sheets which includes means for moving said sheets along a definite path, a tool having an abrasive surface mounted for movement toward and away from said path, and means for driving said tool to move said abrasive surface relative to said path; the improvement which comprises monitoring means operable when one of said glass sheets reaches a predetermined position in said path to move said tool under pressure toward said path and for reducing said pressure when said tool is in working engagement with an edge of one of said sheets, said monitoring means including means responsive to variations in the edge contour of said sheets for varying said pressure to maintain a relatively constant pressure of said tool against said sheet edge during said working engagement.

4. In apparatus for edge treating glass sheets which includesmeans for moving said sheets along a definite path, a tool having an abrasive surface mounted for movement toward and away from said path, and means for driving said tool to move said abrasive surface relative to said path; the improvement which comprises monitoring means operable when one of said glass sheets reaches a predetermined position in said path to move said tool under pressure toward said path and for reducing said pressure when said tool is in working engagement with an edge of one of said sheets, and in which said tool is an endless belt positioned to engage edge corners of said sheets during said working engagement therewith, is associated in tandem with one similarly mounted and operably positioned to engage the opposite edge comers of said sheets and another similar tool positioned to engage the sheet edges lying between said corners, and said monitoring means includes a follower adapted for moving engagement with said sheet edge.

5. Apparatus as defined in claim 3 in which said means for moving said tool comprises a fluid operated device, said monitoring means includes a follower engageable and adapted for moving contact with said sheet edge, and said pressure reducing and varying means comprise a valve operatively connected to said follower for controlling the supply of fluid to said device.

6. Apparatus as defined in claim 5 in which means is provided for resiliently urging said valve toward open position.

7. Apparatus as defined in claim 5 in which said follower is a roller, said operative connection between said valve and said follower includes a shaft upon which said follower is rotatably mounted, a second rotatable shaft parallel with said first shaft, an actuator bar for said valve mounted on said second shaft, and a lever connecting said first and second shafts to impart bodily motion of said follower to said valve actuator bar.

8. Apparatus as defined in claim 4 in which the means for moving said sheets comprise pairs of endless belts engageable with opposite surfaces of said sheets in which each belt includes a series of individual cushioning blocks shaped for interrneshing engagement with adjacent blocks, and means for driving said belts to move said sheets along said path by contact of said blocks with the surfaces thereof. 

1. In apparatus for edge treating glass sheets which includes means for moving said sheets along a definite path, a tool having an abrasive surface mounted for movement toward and away from said path, and means for driving said tool to move said abrasive surface relative to said path; the improvement which comprises monitoring means operable when one of said glass sheets reaches a predetermined position in said path to move said tool under pressure toward said path and for reducing said pressure when said tool is in working engagement with an edge of one of said sheets, said monitoring means including a follower adapted for moving engagement with said sheet edge.
 2. Apparatus as defined in claim 1 in which said monitoring means includes means for holding said tool away from said path under pressure when none of said sheets has an edge in position for working engagement thereby.
 3. In apparatus for edge treating glass sheets which includes means for moving said sheets along a definite path, a tool having an abrasive surface mounted for movement toward and away from said path, and means for driving said tool to move said abrasive surface relative to said path; the improvement which comprises monitoring means operable when one of said glass sheets reaches a predetermined position in said path to move said tool under pressure toward said path and for reducing said pressure when said tool is in working engagement with an edge of one of said sheets, said monitoring means including means responsive to variations in the edge contour of said sheets for varying said pressure to maintain a relatively constant pressure of said tool against said sheet edge during said working engagement.
 4. In apparatus for edge treating glass sheets which includes means for moving said sheets along a definite path, a tool having an abrasive surface mounted for movement toward and away from said path, and means for driving said tool to move said abrasive surface relative to said path; the improvement which comprises monitoring means operable when one of said glass sheets reaches a predetermined position in said path to move said tool under pressure toward said path and for reducing said pressure when said tool is in working engagement with an edge of one of said sheets, and in which said tool is an endless belt positioned to engage edge corners of said sheets during said working engagement therewith, is associated in tandem with one similarly mounted and operably positioned to engage the opposite edge corners of said sheets and another similar tool positioned to engage the sheet edges lying between said corners, and said monitoring means includes a follower adapted for moving engagement with said sheet edge.
 5. Apparatus as defined in claim 3 in which said means for moving said tool comprises a fluid operated device, said monitoring means includes a follower engageable and adapted for moving contact with said sheet edge, and said pressure reducing and varying means comprise a valve operatively connected to said follower for controlling the supply of fluid to said device.
 6. Apparatus as defined in claim 5 in which means is provided for resiliently urging said valve toward open position.
 7. Apparatus as defined in claim 5 in which said follower is a roller, said operative connection between said valve and said follower includes a shaft upon which said follower is rotatably mounted, a second rotatable shaft parallel with said first shaft, an actuator bar for said valve mounted on said second shaft, and a lever connecting said first and second shafts to impart bodily motion of said follower to said valve actuator bar.
 8. Apparatus as defined in claim 4 in which the means for moving said sheets comprise pairs of endleSs belts engageable with opposite surfaces of said sheets in which each belt includes a series of individual cushioning blocks shaped for intermeshing engagement with adjacent blocks, and means for driving said belts to move said sheets along said path by contact of said blocks with the surfaces thereof. 